If you've checked the airgap for any foreign objects and find it clear, the next step would be to connect the discharge to a separate diswasher tailpiece instead of of the disposal. Cap off the disposal and install the dishwaser tailpiece under the second strainer.

: Recently, our dishwasher air vent has begun to spill over onto the countertop when the dishwasher is discharging: waste water. The vent is connected to an Insinkerator Disposal in one section of a dual basin kitchen sink.: The drain does not appear to be obstructed, and all else works okay.: How do I resolve this problem?